四年级数学下册三运算定律与简便计算3简便计算课件.ppt

单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,单击此处编辑母版标题样式,颍泉区宁老庄中心小学,靳海涛,北师大版 六年级数学,9X4+9X6,=36+54,=90,9X(4+6),=9X10,=90,9X(4+6)=9X4+9X6,9,4,6,?,复习导入,a X(b +c)=a X b +a X c,用字母表示乘法分配律：,一个数,乘,两个数的,和,可以把这个数,分别,同这两个数,相乘,再把两个,积相加,结果,不变,.,这叫做,乘法的分配律,.,用字母表示乘法分配律逆定律：,a X b +a X c=a X(b +c),公式总结,1,2,3,4,（,15+37),12=15,37,_,(28+45),7,=_,7+_,7,54,14+46,14=,（,_,+_,）,_,66,28+66,32+66,40,=,（,+,）,12,12,28,66,46,54,14,28,32,40,45,小试牛刀,热身运动,7,5,7,2,=,+,20,20,(,),+,20,7,5,7,2,=,15,2,3,7,15,2,15,2,15,2,3,4,15,2,(,),3,7,3,4,(,7,1,+,),10,1,=,70,7,1,70,+,10,1,70,4,3,),3,1,=,12,=,4,3,12,3,1,12,4,3,12,3,1,4,、,3,、,2,、,4,3,3,1),12,1,、,初显身手,3,2,+,),4,7,=,12,+,（,6,1,3,2,12,+,4,7,12,6,1,12,7,6,48,6,1,=,7,342,6,1,200,199,198,=,200,199,1,（,1,),9,1,31,8,1,8,9,280,=,1,、,2,、,3,、,4,、,=,200,1,200,199,1,=,尝试练习,7,1,),9,1,7,9,(,7,1,),9,1,7,9,(,7,1,),9,1,7,9,(,7,1,),9,1,7,9,(,7,9,),7,1,9,1,(,1,、,2,、,3,、,4,、,活学活用,17,1,+,0.75,+,17,1,4,1,10,9,11,-,10,9,13,7,13,6,29,6,29,22,30,25,19,60,25,3,挑战自我,+,9,8,2007,20082008,2006,20072007,8,1,1,13,7,7,8,+,8,13,1,1,0.08,1.125,112.5,13,3,1,13,12,4,1,、,2,、,